What are General's Bunker and the Crypt? How to heal, to fight or to dance with bosses?

To get the opportunity to fight, heal, dance or cast a spell on a boss you should go through several stages:
1. Dig up the boss lair (asking items to neighbours or buying them).
2. Collect the keys to enter the fight (by banishing the adepts of the boss).
After this you have just to fight, heal, dance or cast a spell using different items from the list (weapons, remedies, dancers or other items). You have a limited numbers of hits, which can be checked under the progress bar. You can fight the boss alone or with the help of your friends, by inviting them to join. Once the battle is successfully completed, you get a chest. The higher your rank, the greater the reward. Note that each battle lasts only for several hours, the timer can be seen under the picture of the boss. In case you do not manage to defeat the Boss within this time, you will have to collect another set of keys and start the challenge again. Hurry up! You have only 2 hours to explore the room after defeating the Boss. When this period of time expires the Boss will come back to his chamber and you will have to fight him again.